The present invention relates generally to the drilling of oil and gas wells, and more specifically, to downhole tools including one or more force application members for centering, positioning, stabilizing, and/or steering downhole tools such as a directional drilling assembly in a well bore.
During the drilling, testing, and completion of oil and gas wells numerous downhole tools are used that utilize radially protruding members that contact the well bore wall to center, position, stabilize, and/or steer the tool in the well bore. For example, in directional drilling applications, which are commonly used to more fully exploit hydrocarbon reservoirs, drill assemblies are typically utilized that include a plurality of independently operable force application members to apply force on the well bore wall during drilling to maintain the drill bit along a prescribed path and to alter the drilling direction. Such force application members are typically disposed on the outer periphery of the drilling assembly body or on a non-rotating sleeve disposed around a rotating drive shaft. One or more of the force application members may be moved in a radial direction, e.g., using electrical or hydraulic devices, to apply force on the well bore wall in order to steer the drill bit outward from the central axis of the well bore.
Prior art downhole tools, such as the Autotrak(copyright) steering tool (available from Baker Hughes Incorporated, Houston, Tex.), typically utilize force application members that are coupled to the tool body at a hinge or pivot. Alternately, such as in the steering tool disclosed by Webster (U.S. Pat. No. 5,603,386), the force application members are not directly coupled to the tool body, but rather to one or more actuators that are in turn mounted on the tool body.
Downhole tools that include force application members typically are further capable of retracting the members inward towards the tool body. Such retraction may be required, for example, at the end of an operation, such as a drilling or survey operation, to allow the tool to be withdrawn from the well bore without becoming lodged therein or damaging the force application members. One drawback with the above described prior art downhole tools, is that they tend to require complex mechanical and/or pneumatic/hydraulic devices for extending and retracting the force application members. Such mechanisms for extending and retracting typically have a number of interoperable moving parts, whose complexity tends to inherently reduce the reliability of the downhole tool. Further, increased complexity tends to increase both fabrication and maintenance costs.
Therefore, there exists a need for downhole tools including improved force application members and/or force application modules. In particular, there exists a need for downhole tools including relatively simple (and therefore relatively inexpensive) force application member mechanisms.
In one aspect this invention includes a downhole tool. The downhole tool includes a tool body and at least one elongated sprung member deployed on an outer surface of the tool body. The sprung member is configured to lie in a rest position substantially parallel to the outer surface. Further, each sprung member includes at least one movable end, which is movable with respect to the tool body. Displacement of the movable end with respect to the tool body causes elastic spring biasing of the sprung member via bending thereof. The downhole tool further includes an actuation module deployed on the tool body, operably engaged with the sprung member, and disposed, upon actuation, to deflect the movable end thereof away from the rest position. The elastic spring biasing urges the sprung member to return to the rest position upon de-actuation of the actuation module. In one variation, the downhole tool is a steering tool for a directional drilling assembly and includes at least three sprung members disposed equi-angularly about the periphery of the tool.
In another aspect this invention includes a method for deflecting a downhole tool in a direction substantially orthogonal to a cylindrical axis of a well bore. The method includes providing a downhole tool as described in the preceding paragraph and lowering the tool into a well bore. The method further includes causing the actuation module to deflect the movable end of the sprung member away from the rest position and into engagement with a wall of the well bore, and de-actuating the actuation module so as to allow the elastic spring biasing to urge the sprung member to return towards the rest position and away from the wall of the well bore.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter, which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should be also be realize by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.